The euphoriant properties and other subjective effects of sedative and stimulant drugs of known and unknown abuse liability will be assessed in casual recreational drug users. Subjects will be studied in groups. Subjective effects will be assessed with the Addiction Research Center Inventory (ARCI), as well as other measures of highness and drug desirability. Diazepam and methaqualone, as standard abusable sedatives, will be compared with other benzodiazepines (prazepam, alprazolam, lorazepam) and placebo in multiple crossover studies. Stimulant drugs to be studied and compared with d-amphetamine will include phenylpropanolamine, ephedrine, and magnesium pemoline. Other newer non-benzodiazepine antianxiety drugs and newer antidepressants may also be studied as they emerge.